China has demarcated an "air-defence identification zone" on Saturday over an area of the East China Sea, covering islands that are also claimed by Japan.

China's Defence Ministry said aircraft entering the zone must obey its rules or face "emergency defensive measures".

In a statement, the Defence Ministry said aircraft must report a flight plan, "maintain two-way radio communications", and "respond in a timely and accurate manner" to identification inquiries.

"China's armed forces will adopt defensive emergency measures to respond to aircraft that do not co-operate in the identification or refuse to follow the instructions," the statement said.

Yang Yujun, a defence ministry spokesman, also said China set up the area with the aim of safeguarding state sovereignty, territorial land and air security, and maintaining flight order, adding that it is not directed against any specific country or target.

 “China has always respected the freedom of over-flight in accordance with international law’’. He declared.

 The zone came into effect from10:00 Japan local time (02:00GMT).

The islands, known as Senkaku in Japan and Diaoyu in China, are a source of rising tension between the countries.

In 2012, the Japanese government bought three of the islands from their Japanese owner, sparking mass protests in Chinese cities.

Since then, Chinese ships have repeatedly sailed in and out of what Japan says are its territorial waters.

In September this year, Japan said it would shoot down unmanned aircraft in Japanese airspace after an unmanned Chinese drone flew close to the disputed islands.

China said that any attempt by Japan to shoot down Chinese aircraft would constitute "an act of war".